The present invention relates to a paste applying method for applying a bonding paste within an application area set on an object to be applied such as substrate or the like.
In die bonding for bonding a chip on a substrate such as a lead frame, a bonding paste is applied on the substrate surface. In a paste applying method, by moving an application nozzle while discharging the paste from the application nozzle by a dispenser, it is drawn and applied in a specified application area on the substrate surface. In this method, the moving route of the application nozzle from an application start point to an application end point is set in the application area set according to the chip shape. This moving route is determined in various shapes depending on the applying pattern, and, for example, in a rectangular application area, a cross shape of moving the application nozzle in an xe2x80x9cxxe2x80x9d-form, or an asterisk shape of overlaying a xe2x80x9c+xe2x80x9d-form on the xe2x80x9cxxe2x80x9d-form may be employed.
In the drawing application by a conventional paste applying apparatus, however, the following problems were involved. First, such cross shape or asterisk shape is formed by combining a plurality of line segments, and the application nozzle is moved up and down every time drawing each line segment, and discharge of paste from the dispenser is started and stopped in every up-down movement. For intermittent paste discharge, it is necessary to set the response time from start-stop command to actual start-stop action of the dispenser, or an allowance time until the state after response is stabilized. Accordingly, as the number of line segments for composing the pattern is increased, the start-stop frequency of discharge is increased, and the rate of start-stop action only and not applying actually by the dispenser increases, and the entire application efficiency is lowered.
Also by frequent repetition of discharge and stop, it leads to fluctuations of application amount, defective shape of application due to stringing phenomenon of a small amount of paste drooping from the nozzle after stopping of discharge, and other problems. Further, for applying by combining multiple line segments, the application lines are overlapped in the central part of the application area, and the paste is built up high, and, as a result, the lower end of the application nozzle touches the paste, which may cause discharge failure. Thus, in the conventional paste applying method, the application efficiency was poor and it was difficult to assure the application quality.
The invention presents a paste applying apparatus and a paste applying method capable of enhancing the application efficiency and assuring the application quality.
The paste applying apparatus of the invention is a paste applying apparatus for applying paste in a rectangular application area set on the surface of the object to be applied.
The applying apparatus comprises:
an applicator having a discharge port for discharging the paste,
a mover for moving the discharge-port relatively to the object,
a memory unit for storing data showing positions of an application start point, a plurality of passing points, and an application end point in the application area, and
a controller for controlling the mover so as to move the discharge port with one continuous line from the application start point to the application end point by way of the plurality of passing points, according to the data in the memory unit. The plurality of passing points are set at each corner of the application area.
The paste applying method of the invention for applying paste in an application area set on the surface of the object to be applied comprises:
(a) a step of supplying the object, and
(b) a step of moving a discharge port of an application nozzle with one continuous line-from an application start point to an application end point along the moving route, and applying the paste on the surface of the object while discharging the paste from the discharge port. The moving route has an undulation pattern of concave and convex shape.
Preferably, the plurality of passing points include a plurality of first passing points and a plurality of second passing points, and the plurality of first passing points are set at each corner of the application area, and the plurality of second passing points are set at the central side of the application area.
Preferably, the moving route of the discharge port has such a shape that the middle point of mutually adjacent corners may be positioned at the most central side of the application area.
Preferably, at least one of the application start point and application end point is positioned on the central point of the application area.
Preferably, the application start point is positioned at a first vicinal position of the central point of the application area, and the application end point is positioned at a second vicinal position of the central point of the application area.
Preferably, the application start point and application end point are positioned near the central point of the application area.
Preferably, the undulation pattern has a convex portion positioned at each corner of the application area, and the concave portion is positioned between the convex portions.
In this configuration, the application efficiency is enhanced. The application quality is also improved.